Self-lowering jack



J. C. KOPF.

SELF LOWERING JACK. APPLICATION HLED FEB. 4. 1921-.

1,397,869, Patented Nov. 22, 1921.

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SELF LOWERING JACK.

APPLICATION FILED rzs.4. 1921..

1,397,869. PatentedNov.22,1921.

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SELF LOWERING JACK.

APPLICATION FILED FEB. 4. 1921.

1,397,869, Patented Nov. 22, 1921-.

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SELF LQWERING JACK.

APPLICATXON man FB.4.192|.

1,397,869, Patented Nov; 22, 1921.

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UNITED STA'I:

RATENT OFFICE.

JOHN C. KOPIF, OF BELLEVUE BOROUGH, PENNSYLVANIA, ASSIGNOR TO THE DUFFMANUFACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION 01PENNSYLVANIA.

SELF-LOWERING J'ACK.

Specification of Letters Patent.

Patented Nov. 22, 1921.

To all whom it may concern:

Be it known that I, JOHN G. Kerr, a citizen of the United States, and aresident of the borough of Bellevue, in the county of AlleghenyandVState of Pennsylvania, have invented a certain new and usefulImprovement in Self-Lowering Jacks, of which the following is aspecification.

In a copending application, Serial No. 419,694, filed Oct. 26, 1920, Ihave disclosed a self lowering screw-jack having a manually-controlledmechanical holding device and a double-acting daslrpotgeared to therotary run-down screw, as therein more particularly set forth. Thepresent invention is specifically an improvement within this type ofjack, affording certain features of advantage having to do with thegeneral purpose of providing a simple, safe and citicient jackmechanism.

In the accompanying drawings, forming part hereof:

Figure 1 is a vertical section through a jack embodying the invention,taken in the plane of the axes of the screw and main operating shaft,which are seen in elevation;

Fig. 2 is a vertical section on a larger scale taken on the line 22 ofFig. 1, showing a portion of the interior mechanism partly in elevationand partly broken away and in section;

Fig. 3 is a horizontal section on the line 3--3 of Fig. 2, with interiorparts in elevation;

Fig. 4 is a vertical section on the line 4-4: of Fig. 2; and

Fig. 5 is a vertical section on the line 55 of Fig. 2.

The jack has a base 1, provided with a hollow standard 2 and an annexchamber 3 toward the bottom. The vertically movable load member ispreferably in the form of a ram 4 slidably guided in a bearing 5 in thetop of the stationary standard of the base, the top of the ram having ahead 6 to act upward against the jacking point of the part to be raised.The ram is held against turning by a key 7 held in the upper part of thestandard and projecting into a vertical groove 8 in the side of the ram.

The ram is hollow and its lower portion holds, or is formed as, a nut 9,or non-rotary screw member. A male screw 10 is supported rotatably onthe base upon a ballv movement of the screw in one direction, the

lifting direction, is produced by oscillatory movement of a removablebar.

The threads of the screw, meaning thereby the two screw members, are tobe understood as being of steep pitch, that is to say,

beyond the angle of repose, so that the jack will run down by itselfunder load, if not held. At such time, through the relative verticalmovement of the rotary and nonrotary screw members, the screw 10 isrotated by the load in the direction reverse to that of lifting, andthis in turn rotates the shaft 12 in the run-down or lowering direction.

An auxiliary shaft 18, for holding and lowering is journaled in bearings19, 20 in the annex chamber, transversely to the main operating shaft;and fixed on this shaft and held against longitudinal movement by thebearings is a worm 21, which meshes with a worm-wheel 22 fixed to themain shaft. The worm-wheel and worm are also of comparatively steeppitch, so that the worm will be rotated by the worm-wheel.

The invention includes a closed singlecylinder and double-acting pistondevice marked generally23, which is shown contained in a barrel 2 1,forming an extension of the annex chamber 3. The said barrel ispreferably provided with an enlarged inner portion which is bolted orotherwise separably secured to the main body of the annex casing. Asthus constructed, a rotary member 26 is rim-journaled, coaxial with theshaft 18, in a bearing-ring 27 inserted in the enlargement 25, and in abearing 28 in the mouth of the annex body. The portion of said memberwhich is held against displacement between these bearings constitutes abrake-drum 29, while the portion or element which extends within thebarrel'is formed with a cam-groove 30. A circular series ofratchet-teeth 31 on the inner face of the member, and a collar 32 withcooperative teeth, slidably keyed on the end ofthe shaft 18 andpressed-by a spring 33, constitute an embodiment of one-way-actingclutch or driving Connection.

Thedrum is encircled by a brake-band, or relatively stationary brakeelement, 34, having perforated end lugs35, which are suspended on a rod36 having bearings in the top of the annex, one of the end portions ofthe rod being a thrust-screw 37 engaging cooperative screw-threads inthe wall, whereby the brake can be released and tightened bymanipulation of an external lever handle 38 on the screw, a spring 89tending to open the band when the screw is backed off.manually-controlled holding and stopping device is thus provided, theprecise form, however, being susceptible of variation.

Fitting slidably in the, barrel 24, and coaxial with the parts whichhave been described, is a closed fluid-tight cylinder 40,

having an extension 41, which telescopes over the cam member 26 and isprovided with cam-follower studs 42 working in the camgroove 30. Thesaid cylinder is held against turning with the rotary cam by screw studs43 in the wall of the barrel projecting inward into longitudinal grooves44 in the exterior of the cylinder.

Within the cylinder is a relatively stationary double-acting piston 45,having a packing-ring 46 making tight sliding contact with the wall. Asillustrated, this piston may be heldstationary in respect to thereciprocation of the cylinder by being connected with the rotary cammember 26, with which it may rotate. As thus arranged, the rod 47 towhich the piston is secured passes through packing glands 48, 49 in theheads of the cylinder and is screwed into the cam member.

An opening 50 of predetermined size through the piston affords arestricted passage between the two chambers at opposite sides, throughwhich the confined fluid in the cylinder, preferably a liquid, isobliged to flow as the cylinder and piston are relatively reciprocated.

In operation, the load is lifted in the usual way, by ratcheting theshaft 12. In this operation, the teeth of the member 30 of the automaticclutch ride idly over the teeth on the brake-drum and cam member 26, thesaid member and the reciprocatory part of the piston and cylinder deviceremaining.

stationary. At the end of each stroke, the effort of the loadtransmitted and reduced through the gearing, and tending to rotate themember 26 in the reverse direction, causesthe clutch to catch, and isthereby solidly sustained by the brake, which remains applied duringlifting. In order to effect lowering, the brake-band is loosened bymeans of the handle 38, thus permitting the brake-drum to turn,whereupon the load member 4- starts to descend. Thereby, through thescrew members, multiplying gears l6, 15, 22 and 21, and the clutch, thecam is rotated, and by it the parts of the coaxial piston and cylinderdevice are relatively reciprocated. This compels the fluid to make itsway back and forth through the restricted passage 50, and thus restrainsthe load member to a safe speed of lowering. Theload can be stopped atany point withgutllnjurious shock by again putting on the ra re.

Other forms and aspects of the inVen tion will suggest themselves to themechanic.

a vertically movable load member, vertical screw means for liftingcomprising a screw which is rotated in one direction to efi ect liftingand in the opposite direction by the act1on of the load in lowering, anda holding devlce, in combination with a cam connected wlth the screw,and a single-cylinder double-acting dash-pot coaxial with the cam andoperable thereby in lowering.

3. A self-lowering jack, having a base and a vertically movable loadmember, vertical screw means for lifting comprising a screw wh ch isrotated in one direction to effect lifting and in the opposite directionby the action of the load in lowering, and a holding device, incombination with a cam connected with the screw, 2. fluid-retardingdevice comprising a riciprocatory cylinder coaxlal with the cam andoperatively related thereto, and a relatively stationary doubleactingpiston in the cylinder.

4. In a self-lowering jack, a base and a vertically movable load member,vertical screw means for lifting comprising a screw which is rotated inone direction to effect lifting and in the opposite direction by theload in lowering, a main operating shaft geared to the screw and bearinga wormwheel, an auxiliary shaft bearing a worm meshmg said worm-wheel, acam coaxial with said auxiliary shaft to be driven thereby, and-afluid-cylinder and piston device coaxial with the cam and operablethereby in lowering.

5. A self-lowering jack, having a base and a vertically movable loadmember, vertical screw means for lifting comprising a screw which isrotated in one direction to effect lifting and in the opposite directionby the action of the load in lowering, and a holding device, mechanismcomprising a multiplying gearing and a one-way-acting clutch connectedwith said screw, a rotary part adapted to be driven through saidmechanism in lowering and comprising coaxial brake and cam elements, arelatively stationary brake member cooperative with said brake element,and a coaxial double-acting single-cylinder dash-pot operable by the camelement.

6. A self-lowering jack, having a base and a vertically movable loadmember, and vertical screw means for lifting comprising a screw which isrotated in one direction to effect lifting and in the opposite directionby the action of the load in lowering, in combination with a cam gearedto said screw, and a device coaxial with the cam, comprising a closedfluid cylinder and a doubleacting piston therein, one of which isoperatively related to the cam.

7. A self-lowering jack, having a base and a vertically movable loadmember, and vertical screw means for lifting comprising a screw which isrotated in one direction to effect lifting and in the opposite directionby the action of the load in lowering, in combination with a cam gearedto said screw, a barrel coaxial with the cam, a closed fluid cylindercontained in the barrel in operative relation to the cam to reciprocatewithout turning in the barrel, and a relatively stationary double-actingpiston in the cylinder.

8. In a self-lowering jack, a base and vertically movable load member,vertical screw means for lifting comprising a screw which is rotated inone direction to effect lifting and in the opposite direction by theaction of the load in lowering, a holding device, and a single-cylinderand doubleacting piston dash-pot device geared to said screw in respectto lowering.

9. In a self-lowering jack, a base and a vertically movable load member,vertical screw means for lifting comprising a screw which is rotated inone direction to effect lifting and in the opposite direction by theaction of the load in lowering, an auxiliary shaft geared to said screw,a rotary member coaxial with said shaft, a one-way-acting connectionbetween said shaft and rotary member, a manual brake cooperative withsaid rotary member, and a piston-and-cylinder retarding device connectedwith said rotary member.

JOHN C. KOPF.

